1. Field of the Invention
This invention relates generally to apparatus for measuring the amount of current flowing through a circuit, and particularly to current detecting device used for detecting current flowing through a circuit formed on a substrate.
2. Prior Art
As is well known in the art, in a current measuring apparatus, a coil is used for generating a magnetic field, and a current is detected by means of a detecting device such as a Hall generator and a magnetoresistor. One example of the current measuring apparatus is disclosed in a Japanese Laid-Open Patent Application No. 53-118175, and FIG. 24 shows an example of such a conventional current detecting device. In this example, a wire line 311, in which a current I' flows, is inserted into a ring-shaped magnetic core 312 around which a coil 313 is wound, and a magnetic field H' made by the current I' is detected by measuring a potential difference between two terminals 314a and 314b of the coil 313.
However, the reactance component of the coil 313 exists in the circuit through which a current, which is to be measured, is flowed thereby undesirably influencing input-output characteristics of the current measuring apparatus. Accordingly, it is difficult to produce a highly accurate current measuring apparatus. In addition, since the coil 313 and the detecting device are difficult to unify as one body, the current measuring apparatus cannot be satisfactorily miniaturized. Besides, in the case of assembly, a further manufacturing step is required for adjusting a gap width between the coil 313 and the detecting device because the gap width is technically difficult to uniform in an assembly line.